Flash memory devices are non-volatile memory media that do not damage stored data even though power is turned off. Flash memory devices are advantageous in having relatively high processing speed such as recording, reading, and deleting, etc. Therefore, flash memory devices have been widely used in data storage for BIOS of PC, a set-top box, a printer, and a network server, etc. Flash memory devices have recent application in devices such as digital cameras, cellular phones, etc. However, as requirements for highly-integrated devices increase, the size of a unit cell of the flash memory device is reduced and a spatial interval between gate areas forming the unit cell is also reduced so that voids are generated when forming a metal wire.
As illustrated in example FIG. 1, a structure of 90 nm flash cells may have bit lines sharing a common source line, the bit lines being configured of 24 bit cells such that unit cells have a horizontal length including cell gates and a vertical length including bit line contacts.
As illustrated in example FIGS. 2(a) and 2(b), a 90 nm NOR flash cell may have a cell size of 0.081 μm2 reduced by about 49% than a 130 nm flash cell. Such a reduction in a cell size may cause problems such as difficulty in patterning important processes forming cells and the generation of voids at the time of gap filling.